Spreading sequence system for full connectivity relay network

ABSTRACT

Fully connected uplink and downlink fully connected relay network systems using pseudo-noise spreading and despreading sequences subjected to maximizing the signal-to-interference-plus-noise ratio. The relay network systems comprise one or more transmitting units, relays, and receiving units connected via a communication network. The transmitting units, relays, and receiving units each may include a computer for performing the methods and steps described herein and transceivers for transmitting and/or receiving signals. The computer encodes and/or decodes communication signals via optimum adaptive PN sequences found by employing Cholesky decompositions and singular value decompositions (SVD). The PN sequences employ channel state information (CSI) to more effectively and more securely computing the optimal sequences.

RELATED APPLICATIONS

This non-provisional patent application is the National Stage ofInternational Patent Application No. PCT/US2015/061084, filed Nov. 17,2015, which claims the priority benefit with regard to all commonsubject matter of earlier-filed U.S. Provisional Patent ApplicationSerial No. 62/080,697 filed on Nov. 17, 2014 and entitled “SPREADINGSEQUENCE SYSTEM FOR FULL CONNECTIVITY RELAY NETWORK”, each of which ishereby incorporated by reference in its entirety into the presentapplication.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under Grant#W911NF-08-1-0256 awarded by the Army Research Office (ARO), Grant#NNX08AV84A awarded by NASA, and the 2014 Air Force Summer FacultyFellowship Program.

FIELD

The present invention relates to systems and methods for generatingspreading pseudo-noise sequences via channel state information (CSI) fortransmitting wireless communication signals.

BACKGROUND

Wireless communication systems suffer from multipath fading especiallywhen the data rate is beyond long-term evolution (LTE)-Advancedstandards. In any terrestrial radio communication system, the signalwill travel directly to a receiver (i.e., a direct path) and/or viarelays and reflections off of buildings, hills, ground, water, and otherobjects (i.e., indirect paths). Selective fading occurs when themultipath fading affects different frequencies across the channel tovarying degrees. As such, the phases and amplitudes of the channelfrequency response will vary over the signal bandwidth. Sometimesrelatively deep nulls may be experienced, giving rise to degraded signalreception. Simply maintaining the overall average amplitude of thereceived signal will not overcome the effects of selective fading, andsome form of equalization may be needed.

To combat multipath fading effects, orthogonal frequency divisionmultiplexing (OFDM) techniques are used in existing 4G LTE and IEEE802.11 WiFi wireless communication systems. OFDM techniques spread thedata over a wideband channel consisting of a large number of narrowbandsubcarriers. When only a portion of the data is lost by nulls of a fewnarrowband subcarriers, the lost data can be reconstituted using forwarderror correction techniques, thus mitigating the effects of selectivemulti-path fading. Code Division Multiple Access (CDMA) schemes such asDirect Sequence Code Division Multiple Access (DS-CDMA) are also used tocombat multipath fading but have not been used significantly for relaynetwork communication systems.

OFDM and DS-CDMA systems using multi-path channels each have knowndrawbacks. For example, CDMA systems using rake receivers exhibitinferior Bit Error Rates (BER) compared to OFDM systems. On the otherhand, OFDM systems completely fail under frequency-offset environments(e.g., Doppler frequency shifts caused by relative mobile movements).

To combat the deleterious effects of multiple-access interference (MAI),the conventional approach in the CDMA scheme has been to employ fixedorthogonal user sequences or signatures with low cross-correlationproperties. However, the orthogonality or desired cross-correlations ofthe transmitted sequences is often destroyed when received at the basestation or the destination due to multi-path fading, inter-symbolinterference, and multi-access interference. Spread-spectrum relaychannels with deterministic (fixed) or random spreading sequences aretypically used. However, these and other strategies do not improve andsecure the signals sufficiently enough for modern communicationrequirements. Another strategy is to obtain pseudo-noise (PN) sequencesby maximizing the signal-to-interference-plus-noise ratio (SINR) withthe maximum eigenvalue principle. However, this approach is not designedfor relay systems and often does not converge.

SUMMARY

Embodiments of the present invention solve the above-mentioned problemsand provide a distinct advance in the art of transmitting data overwireless communication networks. More particularly, the presentinvention provides a system and method for transmitting signals vianon-binary spreading pseudo-noise (PN) sequences dependent on channelstate information of a wireless communication channel.

An embodiment of the present invention is a method of transmitting dataover a wireless communication network. The method broadly includes thesteps of generating a wireless communication signal; dynamicallygenerating first and second non-binary spreading pseudo-noise sequencesvia channel state information of at least one wireless communicationchannel; modulating the signal into an in-phase portion and a quadraturephase portion; overlaying the first non-binary spreading pseudo-noisesequence on the in-phase portion of the signal; overlaying the secondnon-binary spreading pseudo-noise sequence on the quadrature phaseportion of the signal; reforming the signal from the in-phase andquadrature phase portions; and wirelessly transmitting the signal overthe wirelessly communication network. The signal may then be received ata receiving unit, including generating first and second non-binarydespreading pseudo-noise sequences; overlaying the first non-binarydespreading pseudo-noise (PN) sequence on the in-phase portion of thesignal; overlaying the second non-binary despreading pseudo-noisesequence on the quadrature phase portion of the signal; and demodulatingthe in-phase and quadrature phase portions of the signal.

An additional embodiment of the present invention is directed towards asystem of transmitting data over a wireless communication network. Thesystem broadly includes a transmitting unit and a receiving unit. Thetransmitting unit may include a processor for generating a signal,dynamically generating first and second non-binary spreadingpseudo-noise sequences via channel state information of at least onewireless communication channel, modulating the signal, overlaying thefirst non-binary spreading pseudo-noise sequence on an in-phase portionof the signal, and overlaying the second non-binary spreadingpseudo-noise sequence on a quadrature phase portion of the signal. Thetransmitting unit may also include a transceiver for transmitting thesignal over the wireless communication network. The receiving unit mayinclude a transceiver for receiving the signal and a processor forgenerating first and second non-binary despreading pseudo-noisesequences, overlaying the first non-binary despreading pseudo-noisesequence on the in-phase portion of the signal, overlaying the secondnon-binary despreading pseudo-noise sequence on the quadrature phaseportion of the signal, and demodulating the signal.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Other aspectsand advantages of the present invention will be apparent from thefollowing detailed description of the embodiments and the accompanyingdrawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Embodiments of the present invention are described in detail below withreference to the attached drawing figures, wherein:

FIG. 1 is an overall view of a fully connected uplink system inaccordance with an embodiment of the present invention;

FIG. 2 is a schematic illustration of the fully connected uplink systemof FIG. 1;

FIG. 3a is a flow chart of a method of transmitting a signal via thefully connected uplink system of FIG. 1;

FIG. 3b is a continuation of the flow chart of FIG. 3 a;

FIG. 3c is a continuation of the flow chart of FIG. 3 b;

FIG. 4 is an overall view of a fully connected downlink systemconstructed in accordance with another embodiment of the presentinvention;

FIG. 5 is a schematic illustration of the fully connected downlinksystem of FIG. 4;

FIG. 6a is a flow chart of a method of transmitting a signal via thefully connected downlink system of FIG. 4;

FIG. 6b is a continuation of the flow chart of FIG. 6 a;

FIG. 6c is a continuation of the flow chart of FIG. 6 b;

The drawing figures do not limit the present invention to the specificembodiments disclosed and described herein. The drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following detailed description of the invention references theaccompanying drawings that illustrate specific embodiments in which theinvention can be practiced. The embodiments are intended to describeaspects of the invention in sufficient detail to enable those skilled inthe art to practice the invention. Other embodiments can be utilized andchanges can be made without departing from the scope of the presentinvention. The following detailed description is, therefore, not to betaken in a limiting sense.

In this description, references to “one embodiment”, “an embodiment”, or“embodiments” mean that the feature or features being referred to areincluded in at least one embodiment of the technology. Separatereferences to “one embodiment”, “an embodiment”, or “embodiments” inthis description do not necessarily refer to the same embodiment and arealso not mutually exclusive unless so stated and/or except as will bereadily apparent to those skilled in the art from the description. Forexample, a feature, structure, act, etc. described in one embodiment mayalso be included in other embodiments, but is not necessarily included.Thus, the present technology can include a variety of combinationsand/or integrations of the embodiments described herein.

Turning to FIGS. 1 and 2, an uplink relay network system 10 constructedin accordance with an embodiment of the invention is illustrated. Thewireless communication system 10 broadly includes one or moretransmitting units 12 a,b, optionally one or more relays 14 a,b, and areceiving unit 16 for communicating over a wireless communicationnetwork 18. The system 10 may have single-antenna nodes or may be amultiple-input multiple-output (MIMO) relay network system, as describedin more detail below.

The transmitting units 12 a,b generate and transmit wirelesscommunication signals and may be “ground stations”, mobile smartphonedevices, cellular devices, personal digital assistants, tablets,laptops, computers, radios, walkie-talkies, or any other deviceconfigured to communicate over the wireless communication network 18.The transmitting units 12 a,b each may include a processor, a memory, atransceiver, and other computer components and electronic circuitry orhardware for encoding, modulating, and transmitting the signals asdescribed herein.

The processor may implement an application or computer program toperform some of the functions described herein. The application maycomprise a listing of executable instructions for implementing logicalfunctions in the user device. The application can be embodied in anycomputer readable medium for use by or in connection with an instructionexecution system, apparatus, or device. The various actions andcalculations described herein as being performed by or using theapplication may actually be performed by one or more computers,processors, or other computational devices, independently orcooperatively executing portions of the application.

The memory may be any computer-readable medium that can contain, store,communicate, propagate, or transport the application for use by or inconnection with the instruction execution system, apparatus, or device.The computer readable medium can be, for example, but not limited to, anelectronic, magnetic, optical, electro magnetic, infrared, orsemiconductor system, apparatus, device or propagation medium. Morespecific, although not inclusive, examples of the computer readablemedium would include the following: a portable computer diskette, arandom access memory (RAM), a read only memory (ROM), an erasable,programmable, read only memory (EPROM or flash memory), and a portablecompact disk read only memory (CDROM), and combinations thereof.

The relays 14 a,b may be satellites, cellular towers, relay stations,ground stations, repeaters, computing devices (such as the onesdescribed above) acting as relays, or any other unit configured toreceive a wireless communication signal and transmit the signal toanother relay or the receiving unit 16. The relays 14 a,b may also beenvironmental objects such as buildings, ground surfaces, clouds, andother objects.

The receiving units 16 may be any computing device such as the computingdevices described above and are configured to receive communicationsignals. For example, the receiving units 16 may be a “ground station”or other computing device including a processor, memory, transmitter(e.g., transceiver), and/or other electronic circuitry or hardware orcomputer software (as described above) for receiving signals, decodingsignals, and demodulating signals.

The wireless communication network 18 may be any wireless communicationnetwork such as a cloud radio access network (CRAN), a local areanetwork, a wide area network, the internet, an intranet, or wirelessnetworks such as the ones operated by AT&T, Verizon, or Sprint. Thewireless communication network 18 may also be combined or implementedwith several different networks.

Broadly speaking, and with reference to FIG. 2, the uplink relay networksystem 10 may include M number of sources, K number of relays, and onereceiving unit. For purposes of illustration, transmitting unit 12 awill be denoted S₁, and transmitting unit 12 b (the M^(th) source inthis case) will be denoted S_(M). Relay 14 a will be denoted R₁, relay14 b (the K^(th) relay in this case) will be denoted R_(K). Receivingunit 16 will be denoted D for “destination”.

Connections between the sources S₁-S_(M) and the relays R₁-R_(K) and thesources S₁-S_(M) and the receiving unit D are represented by channelmatrices as follows: H_(1,D) is the channel matrix from the source S₁ tothe receiving unit D. H_(1,1) is the channel matrix from the source S₁to the relay R₁. H_(1,K) is the channel matrix from the source S₁ to therelay R_(K). H_(M,D) is the channel matrix from the source S_(M) to thereceiving unit D. H_(M,1) is the channel matrix from the source S_(M) tothe relay R₁. H_(M,K) is the channel matrix from the source S_(M) to therelay R_(K). G₁ is the channel matrix from the relay R₁ to the receivingunit D. G_(K) is the channel matrix from the relay R_(K) to thereceiving unit D.

Turning to FIGS. 3a-c , a signal transmission of the system 10 may beperformed according to the following steps. It will be understood thatsteps may be performed in different orders or simultaneously. Some stepsmay be omitted in certain embodiments and additional steps may beincorporated without limiting the scope of the invention.

First, a transmitting unit 12 may generate a signal from user i, asshown in block 100. In some embodiments, the transmitting unit 12 maymodulate the signal.

For instance, the signal may be encoded, as shown in block 102. That is,the signal may be encrypted or encoded via any other suitable encodingprotocol.

The signal may be then interleaved via an interleaver, as shown in block104. This may make the signal more robust against errors in the signalas it is transmitted over the wireless communication network 18.

The signal may be then modulated into an in-phase portion I₁ and aquadrature phase portion Q₁ via a digital modulator, as shown in block106.

A non-binary spreading pseudo-noise PN sequence generator then generatesa first non-binary (or 1-bit binary) spreading PN sequence, as shown inblock 108. Generation of non-binary (or 1-bit binary) spreading PNsequences will be described in more detail below.

The in-phase portion I₁ portion of the signal may be then overlaid withthe first non-binary (or 1-bit binary) spreading PN sequence, as shownin block 110.

The in-phase portion I₁ may be then filtered through a finite impulseresponse (FIR) filter, as shown in block 112.

The in-phase portion I₁ may then be amplified, as shown in block 114.

The in-phase portion I₁ may then be converted from a digital signal toan analog signal via a digital-to-analog converter, as shown in block116.

The in-phase portion I₁ may then be overlayed with a cosine-basedtrigonometric function such as cos 2π(ƒt), as shown in block 118.

The non-binary spreading PN sequence generator (or another generator)also may generate a second non-binary (or 1-bit binary) spreading PNsequence, as shown in block 120.

The quadrature phase portion Q₁ may then be overlaid with the secondnon-binary (or 1-bit binary) spreading PN sequence, as shown in block122.

The quadrature phase portion Q₁ may then be filtered through an FIRfilter, as shown in block 124.

The quadrature phase portion Q₁ may then be amplified, as shown in block126.

The quadrature phase portion Q₁ may then be converted from a digitalsignal to an analog signal via a digital-to-analog converter, as shownin block 128.

The quadrature phase portion Q₁ may then be overlayed with a sine-basedtrigonometric function such as sin 2π(ƒt) as shown in block 130.

The in-phase portion I₁ and the quadrature phase portion Q₁ may then besummed together into a reformed signal, as shown in block 132.

The signal may then be synthesized to a specific frequency orfrequencies, as shown in block 134.

The signal may then be passed through a band-pass filter (BPF), as shownin block 136.

The signal may then be amplified via an RF amplifier, as shown in block138.

The signal may then be transmitted to the relays R₁through R_(K), asshown in block 140. For example, the signal from the source S₁ may betransmitted to the relays R₁through R_(K) as represented by frequencyselective fading channel matrices H_(1,1) through H_(1,K). The matricesmay be size N×N where N is the PN sequence length.

The signal may be amplified at the relays R₁through R_(K) via RFamplifiers, as shown in block 142. The amplification may be the squareroot of the relay power divided by the received average power.

The signal may be transmitted to the receiving unit D, as shown in block144. As described above, the signal may be transmitted to the receivingunit D from the relays R₁through R_(K) as represented by frequencyselective fading channel matrices G₁-G_(K). The matrices may be size N×Nwhere N is the PN sequence length.

Other signals may be similarly transmitted from source S_(M) to therelays R₁through R_(K) as represented by frequency selective fadingchannel matrices H_(M,1) through H_(M,K), amplified at the relays R₁through R_(K), and then transmitted to the receiving unit D asrepresented by the frequency selective fading channel matrices G₁through G_(K).

Additional signals may be transmitted from the sources S₁ though S_(M)directly to the receiving unit D as represented by direct link frequencyselective fading channel matrices H_(1,D) through H_(M,D), as shown inblock 146.

The signal reaching the receiving unit D may be amplified via an RFamplifier, as shown in block 148.

The signal may be synthesized to a specific frequency or frequencies, asshown in block 150.

The signal may then pass through a BPF, as shown in block 152.

The signal may then be amplified via an intermediate frequency amplifierwith automatic gain control, as shown in blocks 154 and 156.

The signal may then be converted from analog to digital via an analog todigital converter, as shown in block 158. The signal may comprisein-phase portions and quadrature phase portions.

A non-binary despreading PN sequence generator then may generate a firstnon-binary (or 1-bit binary) despreading PN sequence for the in-phaseportions of the signal, as shown in block 160. Generation ofnon-binary1-bit despreading PN sequences will be described in moredetail below.

The in-phase portion of the signal may then be overlaid with the firstnon-binary (or 1-bit binary) despreading PN sequence, as shown in block162.

The in-phase portion of the signal may then be summed over the length ofthe first non-binary (or 1-bit binary) despreading PN sequence, as shownin block 164.

The non-binary despreading PN sequence generator (or another generator)also may generate a second non-binary (or 1-bit binary) despreading PNsequence for the quadrature phase portions of the signal, as shown inblock 166.

The quadrature phase portion of the signal may then be overlaid with thesecond non-binary (or 1-bit binary) despreading PN sequence, as shown inblock 168.

The quadrature phase portion of the signal may then be summed over thelength of the non-binary (or 1-bit binary) despreading PN sequence, asshown in block 170.

The in-phase portion of the signal and the quadrature phase portion ofthe signal may then be demodulated via a digital demodulator, as shownin block 172.

The signal may then be deinterleaved via a deinterleaver, as shown inblock 174.

The signal may then be decoded, as shown in block 176. For example, anencrypted signal may be decrypted.

This results in a completed data transmission, as shown in block 178.

Calculations for signal manipulations for an uplink relay network system(similar to system 10) with two sources, four relays, and one receivingunit will now be described. The receiving unit of such a system receivesthe following signal:

${y_{d} = {\begin{bmatrix}y_{d_{1}} \\y_{d_{2}}\end{bmatrix} = {{H_{{FU}\; 1}s_{1}x_{1}} + {H_{{FU}\; 2}s_{2}x_{2}} + n_{2}}}},{where}$${H_{{FU}\; 1}\overset{\Delta}{=}\begin{bmatrix}H_{s_{1}d} \\{\sum\limits_{j = 1}^{4}{\alpha_{j}H_{r_{j}d}H_{1j}}}\end{bmatrix}},{H_{{FU}\; 2}\overset{\Delta}{=}\begin{bmatrix}H_{s_{2}d} \\{\sum\limits_{j = 1}^{4}{\alpha_{j}H_{r_{j}d}H_{2j}}}\end{bmatrix}},{and}$ $n_{2}\overset{\Delta}{=}{\begin{bmatrix}n_{d_{1}} \\{{\sum\limits_{j = 1}^{4}{\alpha_{j}H_{r_{j}d}n_{r_{j}}}} + n_{d_{2}}}\end{bmatrix}.}$Here, s₁, s₂, x₁, x₂, n_(d) ₁ , n_(d) ₂ , n_(r) _(j) , and α_(j) are,respectively, the non-binary spreading sequence vectors at nodes S₁ andS₂, the transmitted symbols at nodes S₁ and S₂, the AWGN vectors atnodes D₁, D₂, and R_(j), and the scaling factor that preserves powerconstraint P_(R) at relay R_(j),

$\alpha_{j} = {\sqrt{\frac{P_{R}}{E\left\{ {y_{rj}}^{2} \right\}}}.}$

The covariance matrix of noise n₂ is:

$K_{{FU}\; 2} = {\begin{bmatrix}Z_{d_{1}} & 0 \\0 & {{\sum\limits_{j = 1}^{4}{\alpha_{j}^{2}H_{r_{j}d}Z_{r_{j}}H_{r_{j}d}^{H}}} + Z_{d_{2}}}\end{bmatrix}.}$

The receiving unit may process the received signal with two sets ofdespreading sequences, c₁ for symbols from the first source and c₂ forsymbols from the second source. The receiving unit may generate itsestimated symbols of the first and second sources as:{circumflex over (x)} ₁ =c ₁ ^(H) y _(d) =c ₁ ^(H) H _(FU1) s ₁ x ₁ +c ₁^(H) H _(FU2) s ₂ x ₂ +c ₁ ^(H) n ₂,{circumflex over (x)} ₂ =c ₂ ^(H) y _(d) =c ₁ ^(H) H _(FU1) s ₁ x ₁ +c ₂^(H) H _(FU2) s ₂ x ₂ +c ₂ ^(H) n ₂.Here, the superscript H denotes the Hermitian operation, i.e., conjugateand transpose.

A matrix Q_(FU1)

P_(s)H_(FU2)s₂s₂ ^(H)H_(FU2) ^(H)+K_(FU1) may be defined and a Choleskydecomposition may be applied to this matrix as follows: Q_(FU1):Q_(FU1)=A_(FU1)A_(FU1) ^(H). Note that Q_(FU1) is a function of s₂.Then, the spreading and despreading sequences that maximize the SINR forthe first signal branch can be found as s₁ ^(†)=v_(FU1,max) and c₁^(†)=(A_(FU1) ^(H))⁻¹u_(FU1,max), where v_(FU1,max) and u_(FU1,max) arethe right and left singular vectors, respectively, corresponding to themaximum singular value λ_(FU1,max) of matrix A_(FU1) ⁻¹H_(FU1). Thecorresponding maximum SINR can be represented as:

${\max\limits_{s_{1},c_{1}}\gamma_{{FU}\; 1}} = {P_{s}{{\lambda_{{{FU}\; 1},\max}}^{2}.}}$

A matrix Q_(FU2)

P_(s)H_(FU1)s₁s₁ ^(H)H_(FU1) ^(H)+K_(FU2) may be defined and a Choleskydecomposition may be applied to this matrix as follows: Q_(FU2):Q_(FU2)=A_(FU2)A_(FU2) ^(H). Note that Q_(FU2) is a function of s₁.Then, the spreading and despreading sequences that maximize the SINR forthe second signal branch can be found as s₂ ^(†)=v_(FU2,max) and c₂^(†)=(A_(FU2) ^(H))⁻¹u_(FU2,max), where v_(FU2,max) and u_(FU2,max) arethe right and left singular vectors, respectively, corresponding tomaximum singular value λ_(F2,max) of matrix A_(FU2) ⁻¹H_(FU2). Thenon-binary spreading and despreading sequence vectors s₁, s₂, c₁, and c₂can be converted into binary spreading and despreading sequence vectorsby using a simple one-level quantizer for a simple implementation of alow complexity. The corresponding maximum SINR can be represented as:

${\max\limits_{s_{2},c_{2}}\gamma_{{FU}\; 2}} = {P_{s}{{\lambda_{{{FU}\; 2},\max}}^{2}.}}$

Note that Q_(FU1) is for treating the signal from the second source as amultiple access noise, and sequences s₁ ^(†) and c₁ ^(†) may be designedto suppress multiple access interference and noise, and vice versa forQ_(FU2). The despreading sequences are not restricted to the MF type,and they maximize the SINRs using signal and the interference plus noisecomponents. Singular Value Decomposition (SVD) is applied in finding theoptimum despreading sequences. The complexity of the above steps is0(N²) for the global optimum case.

Turning to FIGS. 4 and 5, a second embodiment of the present inventionprovides a downlink relay network system 200 comprising a transmittingunit 202, a number of relays 204 a,b, and a number of receiving units206 a,b. The system 200 may have single-antenna nodes or may be amultiple-input multiple-output (MIMO) relay network system.

The transmitting unit 202 may be similar to the sources described aboveand may be configured to communicate over a wireless network 208. Thatis, the transmitting unit 202 may generate and transmit wirelesscommunication signals and may be a “ground station”, mobile smartphonedevice, cellular device, personal digital assistant, tablet, laptop,computer, radio, walkie-talkie, or any other device configured tocommunicate over the wireless communication network 18. The transmittingunit 202 may include a processor, a memory, a transceiver, and othercomputer components and electronic circuitry or hardware for encoding,modulating, and transmitting the signals as described herein.

The relays 204 a,b may be similar to the relays described above and maybe configured to receive a wireless communication signal and transmitthe signal to another relay or the receiving units 206 a,b. That is, therelays 204 a,b may be cellular towers, relay stations, ground stations,repeaters, computing devices (such as the ones described above) actingas relays, or any other unit configured to receive a wirelesscommunication signal and transmit the signal to another relay or thereceiving units 206 a,b. The relays 204 a,b may also be environmentalobjects such as buildings, ground surfaces, clouds, and other objects.

The receiving units 206 a,b may be similar to the receiving unitsdescribed above. That is, the receiving units 206 a,b may be “groundstations”, mobile smartphone devices, cellular devices, personal digitalassistants, tablets, laptops, computers, radios, walkie-talkies, orother computing devices including a processor, memory, transmitter(e.g., transceiver), and/or other electronic circuitry or hardware orcomputer software (as described above) for receiving signals, decodingsignals, and demodulating signals.

The downlink relay network system 200 may include one source (i.e.,transmitting unit), K number of relays, and M number of receiving units.For purposes of illustration, transmitting unit 202 will be denoted S.Relay 204 a will be denoted R₁, relay 204 b (the K^(th) relay in thiscase) will be denoted R_(K). Receiving unit 206 a will be denoted D₁ andreceiving unit 206 b will be denoted as D_(M).

The source S is connected to the relays R₁-R_(K) and the receiving unitsD₁-D_(M) as represented by channel matrices as follows: H_(S,D,1) is thechannel matrix from the source S to the receiving unit D₁. H_(S,D,M) isthe channel matrix from the source S to the receiving unit D_(M).H_(S,1) is the channel matrix from the source S to the relay R₁. H_(S,K)is the channel matrix from the source S to the relay R_(K). G_(1,1) isthe channel matrix from the relay R₁ to the receiving unit D₁. G_(1,M)is the channel matrix from the relay R₁ to the receiving unit D_(M).G_(K,1) is the channel matrix from the relay R_(K) to the receiving unitD₁. G_(K,M) is the channel matrix from the relay R_(K) to the receivingunit D_(M).

As shown in FIGS. 6a-c , a signal transmission of the system 200 may beperformed according to the following steps. It will be understood thatsteps may be performed in different orders or simultaneously. Some stepsmay be omitted in certain embodiments and additional steps may beincorporated without limiting the scope of the invention.

First, a transmitting unit 202 may generate a signal from user i, asshown in block 300. In some embodiments, the transmitting unit 202 maymodulate the signal.

For instance, the signal may be encoded, as shown in block 302. That is,the signal may be encrypted or encoded via any other suitable encodingprotocol.

The signal may then be interleaved via an interleaver, as shown in block304. This may make the signal more robust against errors in the signalas it is transmitted over the wireless communication network 208.

The signal may then be modulated into an in-phase portion li and aquadrature phase portion Q₁ via a digital modulator, as shown in block306.

A non-binary spreading PN sequence generator may generate a firstnon-binary (or 1-bit binary) spreading PN sequence, as shown in block308.

The in-phase portion I₁ portion of the signal may be overlaid with thefirst 1-bit spreading PN sequence, as shown in block 310.

The in-phase portion I₁ may be filtered through a finite impulseresponse (FIR) filter, as shown in block 312.

The in-phase portion I₁ may also be amplified, as shown in block 314.

The in-phase portion I₁ may be converted from a digital signal to ananalog signal via a digital-to-analog converter, as shown in block 316.

The in-phase portion I₁ may be overlayed with a cosine-based function,as shown in block 318.

The non-binary spreading PN sequence generator (or another generator)also may generate a second non-binary (or 1-bit binary) spreading PNsequence, as shown in block 320.

The quadrature phase portion Q₁ may be overlaid with the secondnon-binary (or 1-bit binary) spreading PN sequence, as shown in block322.

The quadrature phase portion Q₁ may be filtered through an FIR filter,as shown in block 324.

The quadrature phase portion Q₁ may then be amplified, as shown in block326.

The quadrature phase portion Q₁ may be converted from a digital signalto an analog signal, as shown in block 328.

The quadrature phase portion Q₁ may be overlayed with a sine-basedfunction, as shown in block 330.

The in-phase portion I₁ and the quadrature phase portion Q₁ may then besummed together into a reformed signal, as shown in block 332.

The signal may be synthesized to a specific frequency or frequencies, asshown in block 334.

The signal may be passed through a band-pass filter (BPF), as shown inblock 336.

The signal may be amplified via an RF amplifier, as shown in block 338.

The signal may be transmitted to the relays 204 a,b, as shown in block340. For example, the signal may be transmitted to the relays R₁ throughR_(K) from the source S as represented by frequency selective fadingchannel matrices H_(S,1) through H_(S,K). The matrices may be size N×Nwhere N is the PN sequence length.

The signal may be amplified at the relays R₁ through R_(K) via RFamplifiers, as shown in block 342. The amplification may be the squareroot of the relay power divided by the received average power.

The signal may then be transmitted to the receiving units 206 a,b, asshown in block 344. For example, the signal may be transmitted to thereceiving units D₁ through D_(M) from the relays R₁ through R_(K) asrepresented by frequency selective fading channel matrices G_(1,1)through G_(1,M) and G_(K,1) through G_(K,M). The matrices may be sizeN×N where N is the PN sequence length.

The signal may also be transmitted from the source S directly to thereceiving units D₁ through D_(M) as represented by direct link frequencyselective fading channel matrices H_(S,D,1) through H_(S,D,M), as shownin block 346.

The signal reaching one of the receiving units D₁ through D_(M) may beamplified via an RF amplifier, as shown in block 348.

The signal may be synthesized to a specific frequency or frequencies, asshown in block 350.

The signal may pass through a BPF, as shown in block 352.

The signal may be amplified via an intermediate frequency amplifier withautomatic gain control, as shown in blocks 354 and 356.

The signal may be converted from analog to digital via an analog todigital converter, as shown in block 358. The signals may comprisein-phase portions and quadrature phase portions.

A non-binary despreading PN sequence generator then may generate a firstnon-binary (or 1-bit binary) despreading PN sequence for the in-phaseportions of the signal, as shown in block 360.

The in-phase portion of the signal may be overlaid with the firstnon-binary (or 1-bit binary) despreading PN sequence, as shown in block362.

The in-phase portion of the signal may be summed over the length of the1-bit non-binary despreading PN sequence, as shown in block 364.

The non-binary despreading PN sequence generator (or another generator)also may generate a second non-binary (or 1-bit binary) despreading PNsequence for the quadrature phase portions of the signal, as shown inblock 366.

The quadrature phase portion of the signal may be overlaid with thesecond non-binary (or 1-bit binary) despreading PN sequence, as shown inblock 368.

The quadrature phase portion of the signal may be summed over the lengthof the non-binary (or 1-bit binary) despreading PN sequence, as shown inblock 370.

The in-phase portion of the signal and the quadrature phase portion ofthe signal may be demodulated via a digital demodulator, as shown inblock 372.

The signal may be deinterleaved via a deinterleaver, as shown in block374.

The signal may then be decoded, as shown in block 376. For example, anencrypted signal may be decrypted.

This results in a completed data transmission, as shown in block 378.

Calculations for signal manipulations for a relay network with onetransmitting unit, two relays, and two receiving units will now bedescribed.

The signals received at relays R₁ and R₂ are represented by y_(r) ₁ andY_(r) ₂ respectively:y _(r) ₁ =H _(sr) ₁ (s ₁ x ₁ +s ₂ x ₂)+n _(r) ₁ , andy _(r) ₂ =H _(sr) ₂ (s ₁ x ₁ +s ₂ x ₂)+n _(r) ₂ ,where n_(r) ₁ and n_(r) ₂ are the zero-mean complex additive Gaussiannoise vector at R₁ and R₂ respectively. Each has the covariance matrixZ_(r) ₁ =E{n_(r) ₁ n_(r) ₁ ^(H)}=σ_(nr) ₁ ²I_(N) and Z_(r) ₂ =E{n_(r) ₂n_(r) ₂ ^(H)}=σ_(nr) ²I_(N). The received signals at the receiving unitscan be represented as follows:y _(d) ₁ ₁ =H _(sd) ₁ (s ₁ x ₁ +s ₂ x ₂)+n _(d) ₁ ₁, andy _(d) ₂ ₁ =H _(sd) ₂ (s ₁ x ₁ +s ₂ x ₂)+n _(d) ₂ ₁.

A relay R_(j)sends r_(j)=α_(j)y_(r) _(j) to the receiving unit (j=1,2),where α_(j) is the scaling factor that preserves power constraint P_(R)at relay R_(j),

$\alpha_{j} = {\sqrt{\frac{P_{R}}{E\left\{ {y_{rj}}^{2} \right\}}}.}$

The received signals at the receiving units can be represented asfollows:y _(d) ₁ ₂ =H ₁₁ r ₁ +H ₂₁ r ₂ +n _(d) ₁ ₂, andy _(d) ₂ ₂ =H ₁₂ r ₁ +H ₂₂ r ₂ +n _(d) ₂ ₂.

The following terms are defined:T _(FD1)

α₁ H ₁₁ H _(sr) ₁ +α₂ H ₂₁ H _(sr) ₂ ,T _(FD2)

α₁ H ₁₂ H _(sr) ₁ +α₂ H ₂₂ H _(sr) ₂ ,ñ _(d) ₁ ₂

α₁ H ₁₁ n _(r) ₁ +α₂ H ₂₁ n _(r) ₂ +n _(d) ₁ ₂, andñ _(d) ₂ ₂

α₁ H ₁₂ n _(r) ₁ +α₂ H ₂₂ n _(r) ₂ +n _(d) ₂ ₂.

The received signals can thus be represented as:y _(d) ₁ ₂ =T _(FD1)(s ₁ x ₁ +s ₂ x ₂)+ñ_(d) ₁ ₂, andy _(d) ₂ ₂ =T _(FD2)(s ₁ x ₁ +s ₂ x ₂)+ñ_(d) ₂ ₂.

By defining the following:

${H_{{FD}\; 1}\overset{\Delta}{=}\begin{bmatrix}H_{{sd}_{1}} \\T_{{FD}\; 1}\end{bmatrix}},{H_{{FD}\; 2}\overset{\Delta}{=}\begin{bmatrix}H_{{sd}_{2}} \\T_{{FD}\; 2}\end{bmatrix}},{n_{d_{1}}\overset{\Delta}{=}\begin{bmatrix}n_{d_{1}1} \\{\overset{\sim}{n}}_{d_{1}2}\end{bmatrix}},{{{and}\mspace{14mu} n_{d_{2}}}\overset{\Delta}{=}\begin{bmatrix}n_{d_{2}1} \\{\overset{\sim}{n}}_{d_{2}2}\end{bmatrix}},$

the overall received signals at the receiving units D₁ and D₂ can berepresented as:

${y_{d_{1}} = {\begin{bmatrix}y_{d_{1}1} \\y_{d_{1}2}\end{bmatrix} = {{H_{{FD}\; 1}\left( {{s_{1}x_{1}} + {s_{2}x_{2}}} \right)} + n_{d_{1}}}}},{and}$$y_{d_{2}} = {\begin{bmatrix}y_{d_{2}1} \\y_{d_{2}2}\end{bmatrix} = {{H_{{FD}\; 2}\left( {{s_{1}x_{1}} + {s_{2}x_{2}}} \right)} + {n_{d_{2}}.}}}$

The covariance matrices of noise vector n_(d) ₁ and n_(d) ₂ can berepresented as:

${K_{{FD}\; 1} = \begin{bmatrix}Z_{d_{1}1} & 0 \\0 & {{\alpha_{1}^{2}H_{11}Z_{r\; 1}H_{11}^{H}} + {\alpha_{2}^{2}H_{21}Z_{r\; 2}H_{21}^{H}} + Z_{d_{1}2}}\end{bmatrix}},{and}$ $K_{{FD}\; 2} = {\begin{bmatrix}Z_{d_{2}1} & 0 \\0 & {{\alpha_{1}^{2}H_{12}Z_{r\; 1}H_{12}^{H}} + {\alpha_{2}^{2}H_{22}Z_{r\; 2}H_{22}^{H}} + Z_{d_{2}2}}\end{bmatrix}.}$

Then, the receiving units despread the received signals as:{circumflex over (x)} ₁ =c ₁ ^(H) y _(d) ₁ =c ₁ ^(H) H _(FD1) s ₁ x ₁ +c₁ ^(H) H _(FD1) s ₂ x ₂ +c ₁ ^(H) n _(d) ₁ , and{circumflex over (x)} ₂ =c ₂ ^(H) y _(d) ₂ =c ₂ ^(H) H _(FD2) s ₁ x ₁ +c₂ ^(H) H _(FD2) s ₂ x ₂ +c ₂ ^(H) n _(d) ₂ .

Q_(FD1) and Q_(FD2) can denote the covariance matrices of theinterference plus noise vectors as follows:Q _(FD1)

P _(s) H _(FD1) s ₂ s ₂ ^(H) H _(FD1) ^(H) +K _(FD1), andQ _(FD2)

P _(s) H _(FD2) s ₁ s ₁ ^(H) H _(FD2) ^(H) +K _(FD2).

A_(FD1) and A_(FD2) can be defined as the Cholesky decompositionmatrices of covariance matrices Q_(FD1) and Q_(FD2) respectively.Moreover, v_(FD1,max) and u_(FD1,max) can denote the right and leftsingular vectors, respectively, corresponding to the maximum singularvalue λ_(FD1,max) of the matrix A_(FD1) ⁻¹H_(FD1). Also, v_(FD2,max) andu_(FD2,max) can denote the right and left singular vectors,respectively, corresponding to the maximum singular value λ_(FD2,max) ofmatrix A_(FD2) ⁻¹H_(FD2). Then, the sequences that maximize the SINR atreceiving unit D₁ are s₁ ^(†)=v_(FD1,max) and c₁ ^(†)=(A_(FD1)^(H))⁻¹u_(FD1,max) and the corresponding sequences that maximize theSINR at receiving unit D₂ are s₂ ^(†)=v_(FD2,max) and c₂ ^(†)=(A_(FD2)^(H))⁻¹u_(FD2,max). The corresponding SINR can be represented asfollows:

${{\max\limits_{s_{1},c_{1}}\gamma_{1}} = {P_{s}{\lambda_{{{FD}\; 1},\max}}^{2}}},{and}$${\max\limits_{s_{2},c_{2}}\gamma_{2}} = {P_{s}{{\lambda_{{{FD}\; 2},\max}}^{2}.}}$

In summary, embodiments of the present invention include fully connecteduplink and downlink relay network systems comprising one or moretransmitting units, relays, and receiving units connected via acommunication network. The transmitting units, relays, and receivingunits each may include a computer for performing the methods and stepsdescribed herein and transceivers for transmitting and/or receivingsignals. The computers may encode and/or decode communication signalsvia optimum adaptive PN sequences dynamically employing channel stateinformation (CSI). The PN sequences are not available to malicioussignal interferers. The PN sequences may be found by employing Choleskydecompositions and singular value decompositions (SVD). Morespecifically, embodiments of the present invention may employ asignal-to-interference-plus noise ratio (SINR) using single valuedecompositions (SVD) to find the optimum PN sequences. It may be assumedthat channel state information (CSI) is known at a central station suchas a cloud radio access network (CRAN), which can compute and forwardthe optimum PN spreading and despreading sequences to the transmittingunits and receiving units, respectively. Embodiments of the presentinvention find the optimum PN sequences in only a few iteration steps.Embodiments of the present invention may use a half-duplexamplify-and-forward (AF) relay network such that any node in the networkcannot transmit and receive signals simultaneously. Embodiments of thepresent invention may include nodes in an AF-CDMA relay network that aresynchronized through the CRAN.

Although the invention has been described with reference to theembodiments illustrated in the attached drawing figures, it is notedthat equivalents may be employed and substitutions made herein withoutdeparting from the scope of the invention as recited in the claims.

Having thus described various embodiments of the invention, what isclaimed as new and desired to be protected by Letters Patent includesthe following:
 1. A method of transmitting data over a wirelesscommunication network, the method comprising: generating a wirelesscommunication signal; dynamically generating first non-binary spreadingpseudo-noise sequence and a second non-binary spreading pseudo-noisesequence via channel state information of at least one wirelesscommunication channel; modulating the signal into an in-phase portionand a quadrature phase portion; overlaying the first non-binaryspreading pseudo-noise sequence on the in-phase portion of the signal;overlaying the second non-binary spreading pseudo-noise sequence on thequadrature phase portion of the signal; reforming the signal from thein-phase portion and the quadrature phase portion after performingoverlaying; wirelessly transmitting the reformed signal over thewireless communication network; receiving the transmitted signal at areceiving unit; generating first and second non-binary despreadingpseudo-noise sequences; overlaying the first non-binary despreadingpseudo-noise sequence on an in-phase portion of the received signal;overlaying the second non-binary despreading pseudo-noise sequence on aquadrature phase portion of the received signal; and demodulating thein-phase portion of the received signal and the quadrature phase portionof the received signal after performing overlaying.
 2. The method ofclaim 1, further comprising the step of interleaving the signal.
 3. Themethod of claim 1, wherein the first and second non-binary spreadingpseudo-noise sequences are quantized to 1-bitspreading pseudo-noisesequences.
 4. The method of claim 1, further comprising the step offiltering the in-phase portion of the signal through a finite impulseresponse filter.
 5. The method of claim 1, further comprising the stepof amplifying the in-phase portion of the signal.
 6. The method of claim1, further comprising the step of converting the in-phase portion of thesignal from digital to analog.
 7. The method of claim 1, furthercomprising the step of overlaying the in-phase portion of the signalwith a cosine-based trigonometric function.
 8. The method of claim 1,further comprising the step of filtering the quadrature phase portion ofthe signal through a finite impulse response filter.
 9. The method ofclaim 1, further comprising the step of amplifying the quadrature phaseportion of the signal.
 10. The method of claim 1, further comprising thestep of converting the quadrature phase portion of the signal fromdigital to analog.
 11. The method of claim 1, further comprising thestep of overlaying the quadrature phase portion of the signal with asine-based trigonometric function.
 12. The method of claim 1, furthercomprising the step of passing the signal through a band-pass filter.13. The method of claim 1, further comprising the step of amplifying thesignal via a radio frequency amplifier.
 14. The method of claim 1,wherein the step of transmitting the reformed signal includestransmitting the received signal to one or more relays and amplifyingthe received signal at the one or more relays.
 15. The method of claim1, further comprising the step of amplifying the received signal. 16.The method of claim 1, further comprising the step of passing thereceived signal through a band pass filter.
 17. The method of claim 1,further comprising the step of passing the received signal through ananalog to digital converter.
 18. The method of claim 1, furthercomprising the step of deinterleaving the received signal.
 19. A systemfor transmitting data over a wireless communication network, the systemcomprising: a transmitting unit comprising: a processor configured to:generate a wireless communication signal; dynamically generate first andsecond non-binary spreading pseudo-noise sequences via channel stateinformation of at least one wireless communication channel; apply aCholesky decomposition to the signal; apply a singular valuedecomposition to the signal; modulate the signal into an in-phaseportion and a quadrature phase portion; overlay the first non-binaryspreading pseudo-noise sequence on the in-phase portion of the signal;overlay the second non-binary spreading pseudo-noise sequence on thequadrature phase portion of the signal; and reform the signal from thein-phase portion and the quadrature phase portion after performingoverlaying; and a transceiver configured to transmit the reformed signalover the wireless communication network; and a receiving unitcomprising: a transceiver configured to receive the signal transmittedover the wireless communication network; and a processor configured to:generate first and second non-binary despreading pseudo-noise sequences;overlay the first non-binary despreading pseudo-noise sequence on thein-phase portion of the received signal; overlay the second non-binarydespreading pseudo-noise sequence on the quadrature phase portion of thereceived signal; and demodulate the in-phase portion of the receivedsignal and the quadrature phase portion of the received signal afterperforming overlaying.
 20. A method of transmitting data over a wirelesscommunication network, the method comprising: generating a wirelesscommunication signal; encoding the signal; dynamically generating firstand second non-binary spreading pseudo-noise sequences via channel stateinformation of at least one wireless communication channel; modulatingthe signal into an in-phase portion and a quadrature phase portion;overlaying the first non-binary spreading pseudo-noise sequence on thein-phase portion of the signal; overlaying the second non-binaryspreading pseudo-noise sequence on the quadrature phase portion of thesignal; reforming the signal from the in-phase portion and thequadrature phase portion after performing overlaying; synthesizing thesignal to one or more specific frequencies; wirelessly transmitting thereformed signal over the wireless communication network; receiving thetransmitted signal at a receiving unit; generating first and secondnon-binary despreading pseudo-noise sequences; overlaying the firstnon-binary despreading pseudo-noise sequence on the in-phase portion ofthe received signal; overlaying the second non-binary despreadingpseudo-noise sequence on the quadrature phase portion of the receivedsignal; demodulating the in-phase portion of the signal and thequadrature phase portion of the received signal after performingoverlaying; and decoding the demodulated signal.